1. Field of the Invention
The subject invention relates to fiber spin finishes containing fiber lubricants which produce both exceptional lubricity and low residue levels. More particularly, the invention relates to the use of polyoxyalkylene polyethers, prepared by oxyethylating and then oxypropylating ethylenediamine or N,N,N',N'-tetrakis[2-hydroxyalkyl]ethylenediamines, as spin finish lubricants.
2. Description of the Related Art
Fiber finishing compositions are a necessary part of modern, high speed synthetic fiber manufacture. Virtually all operations performed on the fibers following their being spun from the melt require the presence of suitable fiber finishes to prevent snarling and breaking, thus enabling high fiber throughput. Generally speaking, a quality fiber finish must provide several, often conflicting qualities. For example, the fiber finish must qualify both the interaction between the fiber and the machinery on which it is processed, and also the interactions among the fiber filaments themselves. This property is usually termed "lubricity" although in reality the change in the interactions caused by the fiber lubricant may occasionally result in a desirable increase in friction as well as the decrease in friction ordinarily associated with the term "lubricant."
Generally, however, it is desirable for the fiber finish to have high "lubricity," corresponding to a low coefficient of friction. Experimentally, coefficients of friction are measured by applying a solution of the lubricant to a fiber and measuring the coefficient of friction as the fiber is drawn across a satin finished metal spool or pin. One such device in common use for this purpose is the Rothschild "F-meter."
Mineral oil and butyl stearate are commonly used as fiber lubricants because of their excellent lubricity. Unfortunately they have a number of critical disadvantages, making their replacement progressively more important as production technology improves. Among the disadvantages are poor thermal stability and virtually complete insolubility in water. The lack of thermal stability causes a serious air pollution problem as the volatile spin finish boils off the fiber during fiber finishing operations. The lack of water solubility necessitates the addition of emulsifiers, since the lubricants are applied at concentrations of approximately 10 percent by weight in water. The addition of commonly used emulsifiers such as oxyethylated nonyl phenols to the formulation, however, not only increases the complexity of the fiber finish, but due to the relatively high coefficient of friction of the emulsifier itself, the fiber finish emulsion does not retain the advantage of the low coefficient of friction associated with butyl stearate or mineral oil alone.
The use of polyoxyalkylene polyethers themselves as the fiber lubricant component has been proposed as a means of avoiding the necessity of emulsifying a hydrophobic oil. Polyethers containing appreciable amounts of oxyethylene residues, for example, are generally completely water soluble at the concentrations used in fiber finishes. Unfortunately, along with the benefits accorded by water solubility come some disadvantages. Chief among these disadvantages is the much higher coefficient of friction possessed by even the best prior art polyoxyalkylene polyether lubricants, especially those with high oxyethylene group content. The coefficients of friction of many commercial fiber lubricants have been measured using the Rothschild F-meter. Commerical fiber lubricants such as PLURONIC.RTM. polyether polyols and ethylenediamine initiated polyoxypropylene-polyoxyethylene block copolymer polyether polyols which are representative of modern polyether fiber lubricants, have coefficients of friction of from ca. 0.49 to 0.60, averaging approximately 0.55, relative to the 0.35 coefficient of friction of butyl stearate.
A further disadvantage of the nonionic polyether lubricants, one which is shared with lubricants such as mineral oil and butyl stearate, is the necessity to add antistats to the finish composition. The fiber finish composition must be able to control static electricity generated during fiber processing. Generally, ionic organic compounds such as synthetic phosphate and sulfonate detergents are useful as antistats and are added to the fiber finish composition for this purpose. As in the case of the emulsifiers discussed previously, these added antistats do not themselves possess low coefficients of friction. Therefore, their presence, while necessary to control static electricity, causes undesirable changes in the lubricity of the finish.
The fiber finishes are generally applied in the form of an aqueous emulsion by any one of several methods including the use of kiss rolls, sprayers, baths and squeeze rollers, and grooved ceramic guides and metering pumps. To maintain a stable emulsion of the lubricant and antistat components, deleterious surfactants such as fatty alcohol oxyethylates and nonylphenol oxyethylates, as indicated previously, are generally necessary.
A suitable fiber finish must also be easily removable from the fiber or yarn so as not to interfere with subsequent operations such as dyeing and bleaching. Furthermore, since the finish performs its intended functions only on the outside of the fiber, it should not be easily absorbed into the fiber proper. Penetration of the fiber lubricant into the fiber increases the quantity of lubricant required during the finishing operation and, in addition, may cause undesirable changes in the physical properties of the fibers themselves.
As the fiber throughput associated with modern fiber finishing operations has increased, the demands placed upon the fiber finish, especially the lubricant which comprises a major portion of the finish, have increased as well. In drawing and twisting operations, for example, the fiber is drawn across a heater plate, hot draw roll or heated pin in order to raise the temperature of the fiber to the plastic deformation stage. The fibers then undergo stretching, twisting, tangling, or a combination of these operations. The cooled, stretched fiber generally has a much higher tensile strength than the raw fiber. If the fiber has been twisted or tangled in addition to being stretched, it retains these modifications, thus imparting improved feel, fabric cover, recovery from deformation and other properties felt desirable by the textile industry. The fibers may also be textured by processes such as stuffer-tube crimping and edge crimping. These processes also require the fibers to be heated to the same relatively high temperatures as for drawing and twisting, generally in the neighborhood of 190.degree. C. or higher.
As the fiber throughput increases, the temperature of the heating elements must be increased as well in order for the faster moving fibers to be heated to the requisite processing temperatures. Fiber processing machinery is capable of running at speeds in excess of 1000 m/min. At these high speeds, however, the primary heater plate temperature must be maintained at temperatures of 250.degree. C. or higher to enable sufficient heat transfer to the fast moving fibers. At these high temperatures, many prior art lubricants such as butyl stearate and mineral oil volatilize to such an extent so as to leave the fiber with virtually no lubricant coating while at the same time causing a serious fuming problem. Others, particularly the vegetable oils, do not show this high degree of volatility and thus do not leave the fibers totally baren of lubricant at high heater plate temperatures, but instead tend to resinify, causing a rough resinous coating to cover the heater plate. This buildup of resinous coating on the heater plate not only causes decreased thermal transfer from the plate to the fiber but, more importantly, is a primary cause of broken filaments. The need for a fiber lubricant having high lubricity which will neither volatilize too rapidly nor build up resinous deposits at high temperatures has heretofore limited operating speeds to 700 to 800 m/min. In addition to causing broken filaments, the resinous heater plate deposits may adhere to the fibers, causing additional problems such as uneven dyeing in subsequent operations owing to the greater difficulty in removing the resinous by-products as opposed to the unaltered lubricants themselves.
Due to the loss of production time necessitated by cleaning operations or, in some cases equipment replacement, caused by buildup of fiber finish residue, low residue is important even for lower speed operations, or operations with heavy denier fibers. Although the buildup of residue is much slower under the lower temperature conditions of slower fiber finishing, eventually a residue level is reached which requires cleaning and replacement operations to be performed. Thus fiber lubricants which yield low residue are important for both low as well as high speed fiber processing.